A load within a bucket is important for knowing a work amount of a work machine. A technique of computing a load value within a bucket is disclosed for example in Japanese Patent Laying-Open No. 2010-89633 (PTD 1).
In this publication, a current load value of a load is obtained by computing from the attitude of a work machine and the pressure acting on a boom cylinder. By integrating the current load value, an integrated load value is computed. When the integrated load value reaches a target load value, this state is reported to an operator.